First off, if you are using the software commercially in any way, then you need to abide by the terms of the license agreement and use Shop or Pro.
That said, there is a way to get custom colors via RGB, or HSL, or Hex# in Free by assigning your geometry to a Tag. The colors of Tags are adjustable via RGB. Using the color by tag option displays your geometry in that color.
You can also adjust the color and weight of the lines in Free under the styles tab. Again, the colors of the lines are adjustable in RGB.
SO, by using colored lines and color by tag, I was able to make a similar building in custom RGB colors in SketchUp Free.
